For my remaining 225 existing domain user accounts, I need to establish unique SMTP e-mail addresses in the format %username%@alternate.domain, that will then appear in the Exchange Server address book, but these users will NOT have Exchange Server mailboxes. For an individual user, I can right-click and select "Exchange Tasks..." --> "Establish E-Mail Address." Is there a way to do this for 225 existing user accounts using a script of some type?

Thanks, but - that's the wrong approach for me. These are EXISTING user accounts. I do not want to create new contacts for them; I want to "Establish E-Mail Address" under Exchange Server. As far as I know, simply attaching an SMTP address to a contact or an existing user account does not create the global catalog entry that Exchange needs to display that user in the Address Book.

In this video we show how to create a Resource Mailbox in Exchange 2013. We show this process by using the Exchange Admin Center.
Log into Exchange Admin Center.:
Navigate to the Recipients >> Resources tab.: "Recipients" is our default selection …

To show how to create a transport rule in Exchange 2013. We show this process by using the Exchange Admin Center.
Log into Exchange Admin Center.: First we need to log into the Exchange Admin Center.
Navigate to the Mail Flow >> Rules tab.: To cr…